The present invention relates to air-flow fans. More particularly this invention concerns axial-flow fans.
It is known in the art of axial-flow fans to accommodate an impeller within the interior of a casing which has quadrangular outer faces. Such a casing has two opposite end portions, at the inlet and outlet sides of the casing relatively, which are enlarged so as to increase the interior of the casing correspondingly.
Such casings are described in German Pat. No. 1,728,338; U.S. Pat. Nos. 1,642,205; 2,144,035; 1,107,916; 1,719,255; 2,142,307; 2,926,838; 3,029,870; etc.
However, it has been recognized that these constructions are not satisfactory with respect to the requirements made as to optimum utilization of the interior of the casings.